This invention relates to a flexible seal and, in particular, to a flexible seal that is ideally well suited for forming a fluid tight joint between a sewer pipe section and an opening into which the pipe section is fitted.
As disclosed in U.S. Pat. No. 3,787,061 an elastomeric tubular pipe seal is disclosed for joining a pipe section to a manhole riser. A receiving groove that compliments the outer contour of the seal is machined or otherwise formed in the pipe receiving opening of the riser and the seal is seated therein. The pipe section is inserted into the seal opening to complete the joint. A wound spring is contained within an opening formed in the seal which is designed to automatically load against the pipe to lock the seal thereto. The ends of the spring are brought out of the seal and positioned in an expanded chamber formed in the riser. During assembly, the spring ends are engaged by a special tool and the spring is expanded to permit the pipe to be inserted therein. The seal, however, sometimes is pinched or rolled against the sharp edges of the receiving groove during insertion and thus can become torn or otherwise damaged. The expansion of the spring within the limited confines of the opening is oftentimes difficult to achieve. Furthermore, the exposed parts of the spring are susceptible to attack by moisture and other corrosive materials that might be found in and about the seal which can lead to early failure of the seal.
In U.S. Pat. No. 3,958,313, a boot-like seal is disclosed that is also used to join a pipe section to a manhole riser. The boot, as described is a necked down, funnel shaped elastomeric member. In assembly, the neck of the boot is clamped by a metal collar to the pipe section and the wide end of the boot is passed into an opening formed in the riser. The boot is locked to the wall of the opening by means of a special band that includes a toggle joint which, when actuated, expands the band against the inside surface of the enlarged end of the boot. The toggle joins the two ends of the band and normally holds the band in a contracted condition. To expand the band, a closing force of about 1000 psi is exerted by a pneumatic tool directly against the toggle joint. Although the pressure closes the joint, it also destroys the toggle so that the band cannot be released without destroying the unit. Accordingly, if a fluid tight seal is not achieved on the first closure attempt, the seal must be removed from the assembly and replaced with a new unit which, of course, is relatively expensive. By the same token, if the seal must be removed for maintenance purposes or the like, it must be similarly replaced with a new unit. Boot type seals are also highly susceptible to being cut upon the sharp front edge of the riser opening if the connected pipe sections are moved or realigned in the opening. Sharp rocks, tools or other types of foreign objects can also easily penetrate the exposed section of the boot during back filling or excavating operations. Lastly, it should be noted that the expandable band of the seal unit is continually exposed to moisture and other corrosive substances carried by the sewer system and, unless fabricated of special high priced corrosion resistant materials, the bands will fail within a relatively short period of time.